Work ability in patients with polymyositis and dermatomyositis: An explorative and descriptive study

Abstract

BACKGROUND:

Polymyositis (PM) and dermatomyositis (DM) are rare, chronic inflammatory diseases leading to muscle weakness and low muscle endurance. The muscle weakness may lead to restrictions in daily activities and low health-related quality of life.

OBJECTIVES:

This study aimed to investigate the work situation, work ability, work-related risk factors, and influence of the physical and psycho-social work environment in patients with PM and DM.

METHODS:

Patients with PM/DM were assessed using the Work Ability Index (WAI), and the Work Environment Impact Scale (WEIS).

RESULTS:

Forty-eight patients (PM n = 25 and DM n = 23) participated (women/men: 29/19) with a mean age of 54 years (range 28–67 years, SD.10) and mean disease duration of nine years (SD.9). Forty-four percent worked full-time, 31% part-time and 25% were on full-time sick leave. More than 50% self-rated work ability as “poor” or “less good”. Physically strenuous work components were present “quite to very often” in 23–79% and more in patients on sick leave ≥2 years. For those working, the interfering factors in the work environment concerned task and time demands. Supporting factors concerned meaning of work, interactions with co-workers and others. Self-rated work ability correlated moderately–highly positive with percentage of full-time employment, work-related risk factors and opportunities and constraints in the work environment.

CONCLUSIONS:

Poor self-rated work ability is common in patients with PM/DM indicating a need to identify interfering risk factors and support patients to enhance work performance.

Keywords

Work Ability Index (WAI)Work Environment Impact Scale (WEIS)work-related risk factors vocational rehabilitation occupational therapy

1 Introduction

Polymyositis (PM) and dermatomyositis (DM) are rare, chronic inflammatory diseases leading to muscle weakness and low muscle endurance resulting in restrictions in daily activities and low health-related quality of life [1 –3]. These disorders often affect persons of productive age as the majority of the patients are 45–64 years at disease onset with an annual prevalence of 14–17 persons per 100 000 [4]. The disease course varies from severe progressive systemic disease with multi-organ involvement to slowly progressive onset mainly affecting muscle performance [5]. Pharmacological treatment is based on high doses of glucocorticoids in combination with immunosuppressive agents such as methotrexate and azathioprine [5]. The prognosis varies and the overall improvement of muscle performance is slow, over a period of months. Approximately 20% of patients go into remission and recover muscle strength, whereas the majority develops persisting muscle weakness and low muscle endurance that has a negative effect on muscle performance and activities in daily life [1, 6]. For patients with other rheumatic diseases, such as rheumatoid arthritis (RA) or systemic sclerosis, work ability is affected [7, 8]. However, limited information is available on whether PM and DM affect work ability and confers a risk factor for sick leave and early retirement and what risk factors affect work ability. In one previous study, conducted in Hungary, 42% of patients with PM and DM were not able to work at any time from the onset of the disease due to functional impairments and activity limitations caused by the myositis disease [2].

Work in general is important both for the society and the individual since work has positive effects on health and economy [9]. It is of importance to minimize the periods of sick leave because long-term sick leave affects the individual negatively and may result in reduced self-esteem and self-confidence, which makes a return to work more difficult [9, 10]. Work ability has been described by Holm as the relationship between the individual’s resources and job demands [9]. These demands include what type of work it is, what the work incorporates, the organization and the work environment [9 , 12]. Thus reduced work ability is predicted by more physically demanding jobs and older age [11, 13]. If the demands from work are higher than the individual’s resources, the work ability is decreased and needs to be restored, improved or supported [9].

When assessing work ability it is important to consider both objective findings and subjective findings relating to the individual’s resources [14]. The Work Ability Index (WAI) questionnaire covers these aspects and has been validated and found to be a useful tool in predicting work ability for different occupations, such as municipal and construction workers [11 , 14]. Another important aspect to consider is in what way the work environment may pose a challenge for patients with disabilities [12]. The Work Environment Impact Scale (WEIS) was designed to reflect on aspects of the physical and psycho-social environment and how they impact the individual’s ability to return to or remain in employment [12].

Work-related risk factors such as heavy and prolonged or non-varied loads can generate work–related musculoskeletal disorders [15] caused by a repetitive overload of the body [16]. In patients with PM/DM muscle endurance is already reduced [17]. Consequently these patients might be more prone to developing work-related musculoskeletal disorders that restrict work ability compared to the general population.

There is a lack of knowledge concerning objective and self-rated work ability, physical or psycho-social risk factors in the work environment, and what might constitute support or interference to the work ability of patients with PM or DM. With increased understanding of how work ability is affected for patients with PM or DM, appropriate intervention can be applied during treatment or rehabilitation to meet the possible needs to enhance work ability.

The overall aim of the present study was to investigate the work situation, work ability, work-related risk factors, and the influence of the physical and psycho-social work environment and how these factors correlated with each other in patients of working age with PM and DM.

2 Methods

2.1 Study design

This is a cross-sectional, descriptive study including patients with PM and DM in a productive age group enrolled from the longitudinally followed myositis cohort at Karolinska University Hospital in Stockholm, Sweden. The patients were identified in June 2012 from the Swedish myositis registry, SweMyoNet, in which patients have been followed by at least annual assessment of disease activity and medication since 2003. Inclusion criteria in the present study were patients (a) with probable or definite polymyositis and dermatomyositis [18], (b) 18–67 years of age, and (c) alive in June 2012. Exclusion criteria were (a) unable to read and understand questionnaires in Swedish, (b) on sick leave due to other causes than myositis, (c) studying or (d) unemployed.

A letter was sent to eligible patients who were then contacted by phone. Patients who were working or on sick leave less than 2 years and who consented to participate in the study were interviewed in person at Karolinska University Hospital by one of the investigators (MR). Patients who were on sick leave 2 years or more had the questionnaires and consent form sent to them by mail with a prepaid return envelope. If there were questions unanswered, patients were contacted by phone by one of the investigators (MR) to give them the opportunity to complete the questionnaires.

Information on disease activity at time of study was captured from the SweMyoNet and assessed according to the International Myositis Assessment and ClinicalStudies Group (IMACS) [19]. These measures indicated low disease activity by physician’s global assessment of disease activity (0–100 mm) with a mean of 11 (SD. 11) mm and patient’s global assessment of health (0–100 mm) with a mean of 31 (SD. 25) mm. The mean muscle strength measured by MMT-8 (0–80) was 74 (SD. 10), indicating muscle impairment [19].

2.2 Approval

The participants gave written informed consent, according to the declaration of Helsinki, to participate and the study was approved by the regional ethical review board in Stockholm, Sweden.

2.3 Assessments

2.3.1 Information about work situation

Information about work situation was collected using a questionnaire that was designed for this study. This included questions on percentage of full-time employment or sick leave, level of education, number of years at current workplace, changed work task or workplace due to myositis disease, access to and use of assistive devices, and type of work which was classified according to ISCO-08, International Standard of Occupations-08) [20]. The participating patients were subdivided into two groups (a) those working or on sick leave <2 years and (b) those on sick leave for ≥2 years.

2.3.2 The Work Ability Index (WAI)

The Work Ability Index (WAI) was used to assess self-rated work ability [21, 22]. The WAI is a questionnaire that contains seven items (10 questions) that are rated on different scales. One example of these questions concerns the principal demands at work (mentally demanding, physically demanding or a combination of both) [21]. A total score can be calculated by summing the seven items, thus arriving at a total WAI score in the interval of 7–49. A total WAI score of 7–27 indicates “poor” work ability (need to restore work ability), a score in the interval 28–36 indicates “moderate” work ability (need to improve work ability), a score of 37–43 indicates “good” work ability (support work ability) and a score of 44–49 is an indication of “excellent” work ability (maintain work ability) [21, 23]. WAI is a reliable and valid instrument that has been used in several studies since 1981, is translated into 24 languages and has been shown to predict work disability, retirement and mortality [22 , 25]. Both the total WAI score and the responses from five selected questions on aspects of work ability are presented in the results.

2.3.3 Work-related risk factors

The Swedish Work Environment Authority’s statute book (AFS) provision AFS 1998:1 Ergonomics for the Prevention of Musculoskeletal Disorders was used to assess work-related risk factors [16]. Eleven questions were used and were selected based on the symptoms of proximal muscle weakness and reduced endurance that are common in PM and DM [5 , 26]. Self-rating questions concerning work-related risk factors were addressed by asking; how often prolonged or recurrent work is done with arm and shoulder, with neck and back bent, doing fatiguing leg work, with exhaustive manual lifts and carrying or repetitive work movements. The questions were answered by the patients on a four-point scale with rating steps ranging from “never” to “very often”.

2.3.4 The Work Environment Impact Scale (WEIS)

A semi-structured interview instrument, the Work Environment Impact Scale (WEIS) was used according to the manual [27] for individuals who have a job to relate to and it was therefore only used for the subgroup who had been working at some time point during the past two years (n = 38). The WEIS gathers information concerning in what way the person perceives how the work environment supports or interferes with his/her work performance, satisfaction and wellbeing [27]. It contains 17 items that reflect upon the client’s own perception of opportunities and constraints in the work environment related to social groups, physical spaces, objects and tasks [28]. There is an interview guide to follow and complementary questions are used when necessary. After the interview, the assessor rates the 17 items on a four-point rating scale. Ratings 1 and 2 indicate that the item “strongly interferes” or “interferes” with the individual’s work performance, satisfaction and physical/emotional/social well-being, while 3 and 4 imply that the item “supports” or “strongly supports” the individual’s work performance, satisfaction and physical/emotional/social well-being [27]. The environmental factors that interfere and/or provide support are compiled in a summary based on the 17 items [27].

2.4 Statistics

To describe demographics, work situation, self-rated work ability (WAI), work-related risk factors and the work environment (WEIS) mean, standard deviation (SD), median, inter quartile range (IQR), range, number and percent were used.

The Mann Whitney U-test or independent sample t-test were used for group comparisons regarding demographics, work situation, self-rated work ability (WAI) and work-related risk factors.

The Spearman’s rho was used for calculations of correlation between self-rated work ability (total WAI score) and percentage of full-time employment, work-related risk factors and also the work environment (WEIS).

Spearman correlation coefficients between 0 and 0.25 were considered as “no or very low correlation”, 0.26–0.40 as “low correlation”, 0.41–0.69 as “moderate correlation”, 0.70–0.89 as “high correlation”, and 0.90–1.0 as “very high correlation” [29]. For all statistical calculations the Statistical Package for the Social Sciences (SPSS; Chicago, IL) version 19 was used. A statistical significance level of 0.05 was defined.

3 Results

3.1 Participants

By June 2012 there were 78 patients in theSweMyoNet registry who were eligible for the study. Eight patients met the exclusion criteria (Fig. 1). Twenty-one patients did not respond to the letter of invitation or declined participation. Finally, 48 patients were included in the study: 25 with PM (women: n = 17 and men: n = 8) and 23 with DM (women: n = 12 and men: n = 11) (Fig. 1). There was no difference between patients who participated and those who declined participation regarding disease duration, gender or diagnosis, but patients who were excluded were younger compared to those who participated (mean difference 9 years; p = 0.035) (Table 1).

The 48 included patients had a mean age of 54 (SD.10) years and mean disease duration of nine (SD. 9) years and 29 were women (60%). Medical treatment at time of the assessment included glucocorticoids (67%) with a mean daily dosage of 6 (SD. 5) mg and 85% of the patients had various combinations of immunosuppressive agents.

3.2 Information about work situation

Of the 48 patients who were included in the study, 38 had been working during the past two years and 36 of them were working at time of study. Ten patients were on sick leave ≥2 years (range 34–162 months). In the entire group, 44% were working full-time (40 hours/week), 31% worked part time (20–38 hours/week) and 25% were on full-time sick leave (for details see Table 2).

The types of occupations among the participants (n = 48) varied, with the largest proportion (54%) being among the category classified as professionals [20] comprising occupations that require a university degree (Table 2). The second largest group (17%) was the category services and sales workers [20]. For more details see Table 2. The median number of years in the current occupation was 17 years (range, 1–45). Nineteen percent of the patients had changed workplace due to the myositis disease and 33% had changed work tasks for the same reason (Table 2). Seventy-one percent had access to assistive devices at the workplace and of these 82% were using them. The patients who were on sick leave ≥2 years were significantly older (mean difference 11 years; p < 0.001), had longer disease duration (mean difference 7 years; p = 0.04) and had been at the current work place for a longer time (mean difference 12 years; p = 0.014) compared to patients working or on sick leave <2 years (Table 1 and 2).

3.3 Work ability

Sixty-two percent of patients with PM/DM (n = 48) self-rated their work ability as “poor” or “less good”, indicating that their work ability needed to be restored or improved. Thirty-eight percent self-rated their work ability as “good” or “excellent”, indicating that the work ability can be maintained and that they had support for staying in work [21] (Table 3). When patients who were working or on sick leave <2 years were compared to patients who were on sick-leave ≥2 years, the former group of patients perceived their work ability as better (total WAI score) (p = 0.01). Their subjective estimation of current work ability compared to lifetime best was higher (question 1) (p < 0.001), their estimation of impairment due to disease was less (question 5) (p < 0.001) and they experienced a more positive prognosis of work ability two years from now (question 7) (p < 0.001).

Forty-two percent perceived their work to be mostly mentally demanding, while 52% assessed their work to be a combination of both physically and mentally demanding. Sixty-eight percent had more than one week of sick leave during the last 12 months, while 21% had no sick leave (Table 3).

3.4 Work-related risk factors

Several patients (23–79%) reported physically strenuous components in their work “quite often” to “very often” (Table 4). The largest percentage was seen in repetitive work movements (79%), followed by prolonged or recurrent work with arm/hand stretched forward (56%) and neck bent repeatedly or for long periods of time (54%) (Table 4). A larger proportion of patients on sick leave ≥2 years had more often prolonged or recurrent work with arm/hand stretched forward, they were using hand-held machines and were working with pedals, walking stairs and long distances more often than patients working or on sick leave <2 years (Table 4).

3.5 Experience and perception of the work environment

The WEIS instrument was used in patients who were working or on sick leave <2 years (n = 38) [30]. Regarding the WEIS items causing “interference”, 66% of the patients thought that the work tasks at some points were too demanding to handle (Task Demands), in 47% the noise and disturbance in the working area affected the ability to concentrate (Sensory Qualities) and 42% considered the expectations on performance as being too great (Work Role Standard). Furthermore, 41% thought there was a lack of appreciation for the work they performed in the form of salary raise or other career possibilities (Rewards) and 37% did not have enough time to manage the workload (Time Demands) (Fig. 2).

Regarding the WEIS items offering “support”, 97% of the patients considered the co-worker interaction to be a support (Co-worker interaction) as well as the interaction with clients or students, 92% (Interaction with Others). Approximately 95% thought that their work was meaningful and that they thereby made a contribution (Meaning of Work) (Fig. 2).

3.6 Correlations between self-rated work ability and percentage of full-time employment, work-related risk factors and work environment

There was a high positive correlation between self-rated work ability (total WAI score) and a higher percentage of full-time employment (r_s 0.8, p < 0.01) indicating that those who were working full-time tended to experience a better work ability (Fig. 3). Accordingly, 27 patients needed to restore or improve their work ability.

Lower self-rated work ability was moderately correlated to the following work-related risk factors; more frequent occurrence of work with arm/hand stretched forward (r_s 0.79, p < 0.001), forceful movements and uncomfortable hand positions/grips (r_s 0.43, p = 0.003) and repeatedly or for long periods of time back bent forward, backwards, sideways or/and twisted (r_s 0.48, p = 0.001). Moderate to high positive correlations were seen between self-rated work ability and five items of the work environment (WEIS). For example lowerself-rated work ability (total WAI score) was associated with having tasks that were too demanding to handle (Task Demand; r_s 0.7, p < 0.01), not having enough time to manage the workload (Time Demand; r_s 0.5, p < 0.01), not having enough challenges in their work (Appeal to Work Task; r_s 0.5, p < 0.05), excessive expectations on work performance (Work Role Standard; r_s 0.5, p < 0.01) and not having the opportunity to influence working hours (Work Schedule; r_s 0.4, p < 0.05).

4 Discussion

In our study we found that 44% of patients with PM or DM in productive age were working full-time, another 31% worked part-time, while 25% were on full-time sick leave. In this cohort of patients with low disease activity and in most cases with established disease we found that the self-rated work ability was considered as “poor” or “less good” in more than half of the patients and this correlated with a low percentage of full-time employment, some work-related risk factors and support and interferences in the work environment. Physically strenuous components of work were present “quite to very often” and were more commonly present in patients on sick leave ≥2 years. Major interference factors in the work environment, for those working, concerned demands related to both tasks and time. The reported supporting factors for work ability were perception of meaningfulness of work and interactions with co-workers and others.

One aspect of the aim was to investigate the degree of sick leave in patients with PM and DM. The majority of the patients, 75% , were working full- or part-time and 25% were on full-time sick leave. A risk factor for being on sick leave for more than two years was not unexpectedly older age and longer disease duration. In addition the individuals on sick leave experienced more strenuous work involving arms and legs and rated their subjective work ability as being lower compared to those who had been working within the last two years. This may indicate a limitation caused by muscle impairment related to the PM/DM disease, and suggests that patients with this type of work-related tasks may benefit from analysis of work situation and specific support to enhance their ability to continue work.

The 25% of the cohort being on full-time sick leave for more than 2 years is higher compared to the general population (approximately 1.3%) in the Stockholm region at the time of data collection [31]. On the other hand the degree of sick leave was lower in patients with PM/DM compared to results from a multinational study on patients with RA where 37% were on sick leave due to RA [32]. Older age and lower levels of education in patients with RA have been seen as predictors for sick leave [7]. More than half of the patients with PM/DM in this study had a university degree, which could be one explanation why so many were still working. Another explanation for the higher working capacity compared to patients with RA could be that the patients with PM/DM in this study had an established disease with an overall limited muscle impairment and low disease activity at the time of the study. Whether the actual type of work, the fact that 19% of the patients had changed workplace and 33% had changed work tasks due to myositis, or the high presence and use of assistive devices, influenced the work ability and the possibility to stay in work could not fully be answered by the present study.

The self-reported work ability of the 48 patients in the present study was considered as “poor” or “less good” in 62% of patients using the total WAI score. According to the WAI manual, ratings between 7 and 27 (“poor”) indicate a need to have the work ability restored and a rating between 28 and 36 (“less good”) indicates a need for improvement of the work ability (e.g. rehabilitation measures or evaluation of the medical treatment are needed). Notably, ratings in these intervals can be seen as a possible risk factor for future sick leave [13]. Other predictive associations have been seen between reduced work ability measured by WAI and low physical activity, lower health related quality of life, prolonged sick leave and also the ability to determine the need for rehabilitation [33 –35]. We believe that the use of WAI performed in patients with PM/DM might contribute to better care for patients with PM/DM in regards to work performance.

Other studies have only used the score in question 1 in WAI (subjective estimation of the current work ability compared with lifetime best on a scale from 0 to 10) as a measure of self-rated work ability [36, 37] and this has also been used to categorize the self-rated work ability [38]. The patients in our study rated their subjective estimation of the current work ability compared with lifetime best as “poor” with a median value of 7 out of 10. These ratings are comparable to those of patients with RA who also estimated their work ability compared with lifetime best as “poor” but with a median of 4 [36, 37].

Factors that according to the WEIS instrument were perceived as “interfering” with work performance, satisfaction and physical/emotional/social well-being in patients with PM/DM were Task Demand, Rewards and Time Demands, which were in agreement with an earlier Swedish study including patients with musculoskeletal system and connective tissue and mental behavioral disorders who had experience of sick leave [30]. Interfering factors in the work environment among our patients were identified such as tasks being too demanding to handle or not having enough time to manage the workload, difficulties in concentrating due to noise and disturbance in the working area, the expectations on performance as being too great and a lack of appreciation for the work they performed in the form of salary raise or other career possibilities. These interfering factors in the work environment could be beneficial to address in interventions for patients with PM/DM and might possibly improve work ability.

Importantly, the WEIS items Interaction with Others and Meaning of Work were seen as “support” in both the previous and the present study [30]. The highly rated “support” in the work environment regarding interaction with co-workers and others observed in our study might explain why so many of the patients in the subgroup “working or on sick-leave less than two years” were working full-time and had only a few days of sick leave. This finding emphasizes the importance of support at the workplace to continue and improve work participation in patients with musculoskeletal conditions as earlier described [39].

Our results revealed moderate to high correlations between self-rated work ability (total WAI score) and the work environment (WEIS) indicating that strong support in the work environment (WEIS) correlated with higher self-rated work ability (total WAI score) and vice versa emphasizing the importance of the physical and psycho-social work environment for the self-rated work ability.

To cover the areas in the work environment that might be of special interest in patients with PM and DM, work-related risk factors were chosen to address the influence of prolonged and recurrent workload in arms and legs due to the fact that muscle weakness and low muscle endurance in the proximal muscles are common symptoms in PM and DM [5 , 26]. The results of the present study indicate that these manifestations may negatively affect the work ability in these patients [5, 17] and should raise awareness for support and interventions for patients with such work tasks.

Most of the participating patients had some kind of administrative work, including working withcomputers. This might explain the large proportion of possible work-related risk factors found in the categories repetitive work movements, prolonged or recurrent work with arm/hand stretched forward and neck bent repeatedly or for long periods of time. These work-related risk factors might, in the long term, be a risk and negatively affect the work ability in these patients. However, among people working with computers the presence of musculoskeletal symptoms in the arms, shoulder and neck are also influenced by psychological and social job characteristics such as social support [40]. The patients that had not been working during the last two years had more often experienced strenuous work involving arms and legs compared to those still working or on sick leave less than two years, indicating that more strenuous work may be one aspect that negatively affects the ability to remain in work.

One limitation of the present study was the lack of information about the patients who declined participation (27%). Due to the choice of assessment, patients studying or unemployed were excluded. To be studying may be a consequence of the myositis disease, resulting in a need to find more suitable work. However, whether that was the case for the present patients could not be answered by the current study. Another limitation is that we may have underestimated the overall sick leave for patients with PM/DM by using the Swedish myositis registry, SweMyoNet to identify participants. This registry is used for research and patients are asked for consent to be included at the time of the myositis diagnosis. The acceptance rate is almost 100% . However, the most severely ill patients with a high mortality rate may not have been asked for consent. A study on the overall frequency of sick leave would be better to perform using a national, epidemiological approach including registries on diagnoses, national health insurance and sick leave; however, this was not the prime aim of our study.

In conclusion, poor self-rated work ability is common in patients with PM and DM, and there are interfering factors in the work environment that may be related to disease specific impairment of muscle performance affecting the work performance and indicating a need to identify these interfering factors and to support the patients when required to enhance work performance. In the future a study with a qualitative approach would enhance the understanding of the factors that led to permanent sick leave.

Clinical implications of this study are that work-related risk factors should be identified and support should be given to the patients on an individual level (e.g. with information about ergonomics and assistive devices together with recommendations for exercise intervention programs), since physical exercise may improve muscle endurance, fitness and health in patients with PM/DM [41].

Key messages

Based on these results the following clinical implications could be proposed.

Poor self-rated work ability is common in patients with PM and DM.

The work ability in patients with PM/DM needs to be restored or improved.

By addressing interference in the work environment with ergonomic information or assistive devices a therapist may help patients to increase work performance.

Conflict of interest

The authors have declared no conflicts of interest.

Funding

This work was supported by grants from Karolinska University Hospital, Karolinska Institutet (National Health Care Sciences Postgraduate School), the Swedish Research Council, the Swedish Rheumatism Association, King Gustaf V 80-Year Foundation, Funds at the Karolinska Institutet and through the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska Institutet.

Footnotes

Acknowledgments

The authors would like to address their sincerest thanks to the participants. We would also like to thank Christina Ottosson, Inga Lodin and Susanna Farkas for all their help in finding the patients and working with the SweMyoNet registry.

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